Killer immunoglobulin-like receptors (KIR) are a family of receptors that, along with C-type lectin receptors (CD94-NKG2), are used by human NK cells and T-lymphocyte subsets to specifically recognize MHC class I molecules. Certain inhibitory and activating KIR have highly similar extracellular domains and are recognized by the same monoclonal antibody, e.g. KIR2DL1 and KIR2DS1 are both recognized by EB6, and 2DL2 and 2DS2 by GL183.Three criteria (number of extracellular Ig-like domains (domains D0, D1, D2), cytoplasmic tail length, and sequence analogy) have been used to categories the KIR proteins into 13 groups, namely KIR3DL1-2, KIR3DS1, KIR2DL1-5, and KIR2DS1-5.The nomenclature 2D for 2 domains or 3D for 3 domains give the number of Ig-like domains; receptors with either long or short cytoplasmic domains are further classified as L or S. (Pascal V. et al., 2007 J. Immunol 179:1625-1633) The inhibitory receptors possess long (L) cytoplasmic tails (i.e., KIR2DL or KIR3DL) containing a canonical ITIM that becomes tyrosine phosphorylated upon KIR engagement of their HLA class I ligands. The phosphorylated ITIM recruits the Src homology 2 domain containing protein tyrosine phosphatases Src homology 2 domain-containing phosphatase 1 and/or Src homology 2 domain-containing phosphatase 2, which dephosphorylate cellular substrates, thus aborting the NK activation signal, i.e., sparing target cells with appropriate self-MHC class I expression. Receptors with short (S) cytoplasmic tails lack ITIMs (i.e., KIR2DS or KIR3DS). These activating KIR contain a charged residue within their transmembrane domain facilitating interaction with the signaling chain KARAP/DAP12.Engagement of the KIR2DS family of receptors has been shown to lead to a cascade of KARAP/DAP12-mediated signaling events culminating in increased NK cell cytolytic activity and the production of proinflammatory cytokines such as IFN-γ (Pascal et al. 2007) J. Immunol 179: 1625-1633). Mature NK cells are predicted to acquire at least one inhibitory receptor specific for a self-MHC class I molecule, which generally functionally prevails over potentially auto-reactive activating molecules. It is proposed that the response of NK cells represents the integrated outcome of both activating and inhibitory signaling by KIR and other receptors.
KIR3DL2 has been studied as a target for the treatment of malignancies involving CD4+ T cells that express KIR3DL2 receptors, particularly CD4+ T cells, including malignancies such as Mycosis Fungoides and Sezary Syndrome (see, e.g. PCT publications WO2010/081890 and WO02/50122). A ligand of KIR3DL2, HLA-B27, is strongly associated with the Spondyloarthritides (SpA) a group of debilitating inflammatory arthritic disorders typified by Ankylosing Spondylitis (AS). KIR3DL2 ligation by B27 dimers promotes the survival of Th17 and NK cell subsets (Bowness, et al. (2011) Journal of immunology 186:2672-2680; Chan, et al. (2005) Arthritis Rheum 52:3586-3595). It has been shown that that there are increased proportions of pathogenic Th17 and NK cell subsets expressing KIR3DL2 in patients with SpA. Studies strongly suggest that KIR3DL2-B27 interactions have a central role to play in SpA and that KIR3DL2 is a promising therapeutic target.
The existence of antibodies reactive against various KIR3D polypeptides have been reported. The existence of two anti-KIR3DL2 antibodies have been reported: Q241 and Q66 (Pende, et al. (1996) J Exp Med 184:505-518). However, these two antibodies are of the IgM isotype (pentamers) and are not readily suited to pharmaceutical use; furthermore, if their variable regions were placed in the context of a bivalent IgG type antibody, their affinity would be expected to be low. Cells referred to as “AZ158” producing a further antibody was reported (Parolini, S., et al. (2002) In Leucocyte typing VII. D. Mason, editor. Oxford University Press, Oxford. 415-417; PCT publication WO2010/081890). Antibody 5.133 is available from Miltenty Biotech (Auburn Calif.). Both antibodies AZ158 and 5.133 bind KIR3DL2 as well as KIR3DL1 (and further the highly homologous KIR3DS1). KIR3DL2 and KIR3DL1 share relatively high amino acid identity and various HLA ligands that bind KIR3DL2 are also recognized by KIR3DL1.Despite immunizations that gave rise to AZ158, Q241 and Q66, there is a need for improved antibodies in therapeutic and other applications.